Effect of moisture and orientation on the fracture of nylon 6,6 fibers

The effect of relative humidity on the fracture of single nylon 6,6 fibers is determined using fracture mechanics. The fracture energy release rate, G_Ic, of these fibers is shown to be 8× that for injection-molded nylon 6,6 at 0% RH. G_Ic varies from 31.3 kJ/m² at 0% RH to 15.6 kJ/m² at 100% RH. The dependence of G_Ic on RH is in agreement with previous studies indicating two types of water in nylon: a tightly bound and a loosely bound type. In addition, G_Ic is shown to be 10× greater for transverse fiber breaks than for axial splitting of the fiber due to the high degree of orientation in these fibers. These studies are the first of their kind for organic fibers. © 1994 John Wiley & Sons, Inc.     

Charge location effect on the hydration properties of synthetic saponite and hectorite saturated by Na, Ca cations: XRD investigation

This paper aims at comparing the effect of charge location on the hydration properties of two trioctahedral synthetic minerals: saponite and hectorite. The samples were characterised by a layer charge of 0.4 charge per half unit cell and were saturated with Na⁺ or Ca²⁺. The hydration behaviour was studied by determining the structural characteristics which were obtained by modelling XRD patterns.XRD patterns were recorded under controlled relative humidity (RH). The hydrated states of Ca-hectorite were more homogeneous than those of saponite whereas the transition from 1W to 2W occurred at lower RH rates for saponite than for hectorite. For heterogeneous samples, the 1W and 2W layers were stacked randomly fashion for hectorite. Na-saponite-0.4 and Ca-saponite-0.4 were made up of types of layer; one water layer (1W) and two-water layers (2W). The stacking of these layers showed some segregation.     

Urea and formamide as a mixed plasticizer for thermoplastic starch

Mixtures of urea and formamide were tested as plasticizers for thermoplastic starch (TPS). The hydrogen bonding interactions between urea/formamide and starch were investigated by using Fourier‐transform infrared spectroscopy (FT‐IR). The thermal stability, mechanical properties and starch retrogradation behavior were also studied by thermogravimetric analysis (TGA), tensile testing and X‐ray diffraction (XRD), respectively. TPS plasticized by urea (20 wt%) and formamide (10 wt%) showed better thermal stability and water resistance than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and energy at break, respectively, reached 4.83 MPa, 104.6 % and 2.17 N m after storing in an atmosphere of relative humidity (RH) of 33 % for one week. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch. Copyright © 2004 Society of Chemical Industry     

Effects of Relative Humidity on the Ultraviolet Induced Inactivation of Airborne Bacteria

Ultraviolet germicidal irradiation (UVGI) as an engineering control against infectious bioaerosols necessitates a clear understanding of environmental effects on inactivation rates. The response of aerosolized Serratia marcescens, Bacillus subtilis, and Mycobacterium parafortuitum to ultraviolet irradiation was assessed at different relative humidity (RH)levels in a 0.8 m³ completely-mixed chamber. Bioaerosol response was characterized by physical factors including median cell aerodynamic diameter and cell water sorption capacity and by natural decay and UV-induced inactivation rate as determined by direct microscopic counts and standard plate counts. All organisms tested sorbed water from the atmosphere at RH levels between 20% and 95% (up to 70% of dry cell mass at 95% RH); however, no concomitant change in median aerodynamic diameter in this same RH range was observed. Variations in ultraviolet spherical irradiance were minor and not statistically significant in the 20-95% RH range. Cell water sorption and inactivation response was similar for each of the pure cultures tested: when RH exceeded approximately 50%, sorption increased markedly and a sharp concurrent drop in UV-induced inactivation rate was observed.     

Comparative properties of hyaluronan and chitosan in aqueous environment

In this paper, our objective is to compare the physico-chemical properties of chitosan (CHIT) and hyaluronic acid (HA), two important polysaccharides often used in biomedical or cosmetic applications. Polymer-polymer interactions as well as polymer-solvent interactions, studied by experiments and by molecular modeling, are discussed for the two biopolymers in presence of aqueous environments. HA and CHIT have similar non-freezing water content, although HA retains more water than CHIT at large degree of relative humidity (RH). Thermal degradation is larger for HA. The specific viscosity at zero shear rate of CHIT deviates from the master curve, whereas that of HA superimposed nicely. The solution viscosity of concentrated solutions of CHIT continuously decreases in the shear rate range between 0.5 up to 100 s^?1, whereas HA shows a Newtonian plateau at low shear rates. Dynamic rheology of semi-diluted solutions of HA shows storage modulus G?? lower than the loss modulus G?? up to 30 g/L but that of CHIT at 20 g/L shows G?? > G?? at nearly the same overlap parameter. The viscosity of CHIT solution is less influenced by temperature than that of HA. These results clearly underline the importance of interchain interactions for CHIT in a good solvent. Molecular modelling is used to provide insights on both the aggregated state and solution state of the two polysaccharides. Interchain interactions in the organized models were predicted larger for CHIT than for HA whereas the interaction between the polysaccharide and the solvent molecules are larger for HA than for CHIT. This approach rationalizes the experimental observations: the higher solvation of HA and the higher ability to aggregate for CHIT.     

The frost resistance of concrete subjected to a deicing agent

This paper deals with the effect of a deicing agent (NaCl) at different solution concentrations $\text{(1}\text{1}\text{2}\text{, 3,}\text{and}\text{10\%)}$ on the amount of water retained in different types of concrete under various ambient conditions (30%, 47%, 72% and 88% RH) and the resultant frost resistance of concrete treated in this manner. Concrete specimens saturated at the higher salt concentrations were found to retain higher levels of saturation for any given relative humidity condition. However, even when the concretes were conditioned in an atmosphere as high as 88% RH, their retained moisture contents were below critical levels, from the viewpoint of frost resistance.     

Water absorption and proton conductivity of sulfonated acrylamide copolymers

Copolymers of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N-tert-butylacrylamide (tBAA) have been evaluated as proton conducting materials. The water absorption of copolymers with varying equivalent weights (EW), i.e. g polymer/mol sulfonic acid groups, was studied at different relative humidities (rh) by gravimetry and calorimetry. Melt endotherms for water were detected by DSC in copolymers containing ≥45 mol% AMPS when equilibrated at 93% rh, and ≥36 mol% AMPS when equilibrated at 98% rh. A study of the kinetics of the water absorption at 98% rh showed that equilibration was faster for the copolymers than for the homopolymer PAMPS. The proton conductivity (σ) of the samples was investigated as a function of temperature, water content, and EW. ac Impedance measurements between −20 and 70 °C showed a value of σ as high as 0.2 S/cm at 70 °C for a copolymer containing 54 mol% AMPS equilibrated at 98% rh. It was concluded that both the EW and the amount of water in the polymers controlled the conductivity at all temperatures. For example, increasing amounts of water in the polymers generally gave increasing σ above the melting point of the water, but decreasing σ below the same temperature.     

Synthesis and properties of imidazole-grafted hybrid inorganic-organic polymer membranes

Imidazole rings were grafted on alkoxysilane with a simple nucleophilic substitute reaction to form hybrid inorganic-organic polymers with imidazole rings. Proton exchange membranes (PEM) based on these hybrid inorganic-organic polymers and H₃PO₄ exhibit high proton conductivity and high thermal stability in an atmosphere of low relative humidity. The grafted imidazole rings improved the proton conductivity of the membranes in the high temperature range. It is found that the proton conductivities increase with H₃PO₄ content and temperature, reaching 3.2 × 10⁻³ S/cm at 110 °C in a dry atmosphere for a membrane with 1 mole of imidazole ring and 7 moles of H₃PO₄. The proton conductivity increases with relative humidity (RH) as well, reaching 4.3 × 10⁻² S/cm at 110 °C when the RH is increased to about 20%. Thermogravimetric analysis (TGA) indicates that these membranes are thermally stable up to 250 °C in dry air, implying that they have a good potential to be used as the membranes for high-temperature PEM fuel cells.     

Novel biocomposites based on wheat gluten and rubber wood sawdust

Rubber wood sawdust (RWS) was used as a reinforcement for wheat gluten based bioplastics. The RWS content was varied from 0, 5, 10, 15–20 wt %. Effects of the RWS content on the morphology, water absorption, mechanical, thermal, and biodegradation properties of the wheat gluten based bioplastic were investigated. An addition of RWS caused an improvement of the tensile strength and water resistance of the wheat gluten based bioplastics. Scanning electron micrograph of the wheat gluten/RWS composites with a 10 wt % of RWS revealed a good dispersion and uniform embedding of the RWS within the wheat gluten matrix. Agglomeration of RWS was observed when the RWS loads were increased (15 and 20 wt %). The biodegradation process of the composites depended on the amount of RWS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43705.     

EFFECTS OF GLYCEROL ON THE DRYING OF GELATIN AND SUGAR SOLUTIONS

ABSTRACT

The water diffusion coefficients D of gelatin, sucrose arid maltodextrin solutions were determined from the isothermal drying (desorption) rates as a function of water content u ( 0.1 < u < 1.0 ) and temperature (303, 323K) for various glycerol contents ( W_G = 0 – 0.43 kg-glycerol/kg-total solid). When W_G was above 0.2, D increased especially at low water contents (u < 0.25). The desorption isotherms were measured for the same systems. The equilibrium water content at a given water activity A_w decreased with an increase in W_G when A_w < 0.5. This indicates that adding glycerol weakens the water-solute interaction especially at low water contents. Glycerol also softened gelatin films and resulted in loss possibilities of surface cracks during drying.     

Molecular mobility in wool fibers as determined from nuclear magnetic resonance studies

The mobility of protons in wool samples of Lincoln, Chokla, and Merino, equilibrated to various moisture contents in the range of 0–98% relative humidity (RH), have been studied by pulsed nuclear magnetic resonance (NMR) technique. Peak height and peak width were determined from absorption and derivative curves and the relaxation times T₁ and T₂ were determined from relaxation curves. The mobility increases with increase in moisture content. Among the three wools, the mobility was high in Merino as compared to the other two wools. The differences in the measured mobilities were related to structural and morphological differences in the three wools. The present analysis suggests that water in wool has at least three different associations, each with a different binding energy.     

Molecular mechanisms involved in creep phenomena of paper

The phenomenon of mechanosorptive creep (i.e., the increasing creep occurring in some hygroscopic materials subjected to moisture cycling) was studied for paper from a molecular point of view. Paper was tested in creep at different loading levels in a constant high humidity of 90% relative humidity (RH) and in a cyclic climate between 30 and 90% RH. Throughout the creep tests, spectra from the mid‐ and near‐IR, as well as dynamic mechanical data, were recorded to determine molecular changes occurring with time. In tensile stress scans the instantaneous, dynamic elastic modulus was found to increase. It is suggested that this increase was due to orientation of the cellulose molecules, which was detected as changes in the mid‐IR spectra at 1160 cm⁻¹ assigned to the C₁ O C₄ stretching. During creep in constant and cyclic humidity, the modulus was found to increase with time, more so for the cyclic humidity. Changes in the mid‐IR spectra at 1184 and 1030 cm⁻¹, which is assigned to CH₂, CH, and C O, may indicate sliding between the cellulose chains. The near‐IR measurements mainly showed differences in the moisture content. In stress scans the moisture content increased with increasing tensile load. In creep at constant 90% RH, the moisture content was also found to increase in a manner similar to the stress scan. In the cyclic humidity with a conditioning time of 70 min at 90% RH the moisture content decreased successively with increasing numbers of cycles. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1590–1595, 2001     

Effects of high relative humidity on the dynamic adsorption of dimethyl methylphosphonate (DMMP) on activated carbon

The effects of high relative humidity (RH) on the breakthrough of the nerve agent simulant dimethyl methylphosphonate (DMMP) vapor in beds of ASC-impregnated, activated carbon were investigated. Maximum concentrations of DMMP at room temperature and RH > 60% were found to be lower by more than an order of magnitude than in dry air. The breakthrough time (t_B) of 1.2 × 10⁻⁴ g l⁻¹ DMMP in pre-humidified beds and humid air of RH = 90% was shortened by a factor of 1.6 relative to adsorption in dry beds and dry air. Analysis of the breakthrough curves according to the Wheeler–Jonas model indicated that the high RH lowered the dynamic adsorption capacity (W_E) but had nearly no effect on the critical bed weight (W_C). The reduction of W_E by humidity correlates with the observed displacement of adsorbed water by DMMP. The use of DMMP for testing filter performance is limited to low and intermediate relative humidities. On the other hand, DMMP in dry air can be used to advantage for testing the capacity of new or used respirator filters and for the detection of filter channeling.     

Protein/glycerol blends and injection‐molded bioplastic matrices: Soybean versus egg albumen

Two well‐known proteins have been selected in order to produce bioplastics through injection molding: a soy protein isolate (SPI) and an egg white albumen concentrate (EW). Each of them has been thoroughly mixed with glycerol (40 wt %) and the blend then obtained have been characterized by means of rheological and thermomechanical techniques, which allowed the optimization of the processing moulding conditions (cylinder temperature, 60°C–65°C; mould temperature, 120°C; post‐injection pressure, 500–600 bars). Once bioplastics were obtained, their thermomechanical and tensile properties, as well as their water uptake capacity and transparency were evaluated. Bioplastics containing EW showed higher values in the elastic and loss moduli, E′ and E″, from ?30°C to 130°C, than the corresponding SPI bioplastic. However, they both showed qualitatively the same evolution with temperature, where E′ and E″ decreased up to a plateau at high temperatures. When examining their tensile and water uptake properties is found that SPI bioplastics are more ductile and present enhanced water uptake behavior over EW bioplastics, which on the other hand possess higher Young's modulus. SPI seems to provide tougher bioplastics, being an excellent option for potential superabsorbent applications, whereas EW would suit for those applications requiring higher mechanical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42980.     

Protein‐based bioplastics and their antibacterial potential

The use of conventional petroleum‐based plastics in many applications poses the risk of contamination, potentially causing infection when used in medical applications, and contamination when used in food packaging. Nontraditional materials such as protein are being examined for their potential use in the production of bioplastics for applications that require uncontaminated materials. The proteins of albumin, soy, and whey provide possible sources of raw material for bioplastic production, as they have already been utilized in the area of edible films and low‐stress applications. We conducted this study to investigate the thermal, viscoelastic, and antibacterial properties of the albumin, soy, and whey bioplastics with the use of three plasticizers—water, glycerol, and natural rubber latex (NRL). Bacillus subtilis and Escherichia coli were utilized as Gram (+) and Gram (?) species, respectively, for antimicrobial analysis. Albumin and whey bioplastics exhibited similar thermal and viscoelastic properties, whereas soy bioplastics had varied viscoelastic properties based on the plasticizer used. In terms of antibacterial activity, the albumin–glycerol and whey–glycerol were the best bioplastics, as no bacterial growth was observed on the plastics after 24 h of inoculation. In terms of the future impact of this research, the aim will be to scale up production of the bioplastics for use in food packaging as well as biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41931.     

One-Pot Process: Microwave-Assisted Keratin Extraction and Direct Electrospinning to Obtain Keratin-Based Bioplastic

Poultry feathers are among the most abundant and polluting keratin-rich waste biomasses. In this work, we developed a one-pot microwave-assisted process for eco-friendly keratin extraction from poultry feathers followed by a direct electrospinning (ES) of the raw extract, without further purification, to obtain keratin-based bioplastics. This microwave-assisted keratin extraction (MAE) was conducted in acetic acid 70% v/v. The effects of extraction time, solvent/feathers ratio, and heating mode (MAE vs. conventional heating) on the extraction yield were investigated. The highest keratin yield (26 ± 1% w/w with respect to initial feathers) was obtained after 5 h of MAE. Waste-derived keratin were blended with gelatin to fabricate keratin-based biodegradable and biocompatible bioplastics via ES, using 3-(Glycidyloxypropyl)trimethoxysilane (GPTMS) as a cross-linking agent. A full characterization of their thermal, mechanical, and barrier properties was performed by differential scanning calorimetry, thermogravimetric analysis, uniaxial tensile tests, and water permeability measurements. Their morphology and protein structure were investigated using scanning electron microscopy and attenuated total reflection-infrared spectroscopy. All these characterizations highlighted that the properties of the keratin-based bioplastics can be modulated by changing keratin and GPTMS concentrations. These bioplastics could be applied in areas such as bio-packaging and filtration/purification membranes.     

Interaction between water and polytrans-2,5-dimethylpiperazin thiofurazanamide films

Dense films of polytrans-2,5-dimethylpiperazin thiofurazanamide (DMP-TFZ) were characterized as to their physical properties and sorption isotherms. They appeared to be amorphous, endowed with high Tg (247°C), and high mechanical stiffness.Sorption and desorption equilibrium curves were obtained at 23°C for samples 26 and 36 μm thick; hysteresis phenomena were observed only in the desorption steps. BET and Burhoff-Pusch theories and best fit calculations allowed to find that the water layers on the active sorption centers are n = 5 and 1.6 respectively.The Zimm water cluster integral G₁₁/v₁ shows that water tends to be split in single adsorbed molecules in a large field of activities, but that cluster formation is unavoidable in the presence of liquid water. Infrared analysis of the OH stretching region of films conditioned at different relative humidity (RH), demonstrates that water hydrogen bonds in the sorbed state are weaker than in the liquid state and that the presence of big water clusters able to dissolve salts must be excluded. The close packing and high rigidity of the chains should be responsible for the free volume small size holes and uniform distribution, which does not allow big water clusters.     

Synthesis and properties of sulfonated copoly(p-phenylene)s containing aliphatic alkyl pendant for fuel cell applications

A series of novel copoly(p-phenylene)s (PPs) containing an alkyl pendant were successfully synthesized via Ni(0)-catalyzed coupling polymerization. Sulfonated copolymers (SPPs) were achieved by postsulfonation from concentrated H₂SO₄. SPPs showed good solubility in polar aprotic solvents and gave flexible, tough, and transparent free-standing films by solvent casting. The ion exchange capacities (IECs) of the membranes ranged from 2.50 to 2.65 meq/g. All SPP membranes displayed proton conductivity similar to or higher than that of Nafion, especially at high relative humidity (>70% RH) (SPP-1: 0.271 Scm⁻¹, SPP-2: 0.284 Scm⁻¹, SPP-3: 0.212 S cm⁻¹, Nafion: 0.127 Scm⁻¹; at 80 °C and 95% RH). They also exhibited acceptable water uptake in the range of 52-56 vol% at 80 °C with little dimensional change. The gas permeability of the SPP membranes was much lower than that of Nafion 112. Therefore, these materials are promising for fuel cell application.     

γ‐Radiation‐Induced Graft Copolymerization of Ethyl Acrylate onto Hydroxypropyl Methylcellulose

Summary: Graft copolymerization of EA onto water‐soluble HPMC was carried out using γ‐radiation using both simultaneous and preirradiation in an aqueous medium. The effects of radiation environment, radiation dose, monomer concentration, and reaction temperature on percentage of grafting (G) and grafting efficiency (G_E) were investigated. For preirradiation, the observed values for G and G_E were higher in air than in a nitrogen atmosphere. G and G_E values are obviously higher for preirradiation; their maximum values were obtained for a radiation dose of 1.8 kGy. The grafting parameters increase for increasing monomer concentration up to 0.15 mol · L^?1, where they reach their saturation values. In the case of preirradiation, the largest grafting parameters are obtained at 65 °C. The graft copolymers obtained were characterized by FTIR spectroscopy, TEM, SEM, and XRD methods. The method of irradiation significantly affects the mechanical properties of the grafted HPMC samples. Samples prepared by simultaneous irradiation show superior mechanical properties. In addition, the equilibrium humidity adsorption behaviors of the grafted copolymers were also studied, and the humidity resistance behavior of HPMC was enhanced through the grafting copolymerization.

Transmission electron micrograph of the HPMC‐g‐PEA water dispersion.     

Effect of Plasticizers on the Moisture Migration Behavior of Low-Amylose Starch Films during Drying

We report the synergistic and competitive interactions between multiple plasticizers in plasticized low-amylose starch that result in either enhanced or reduced water migration fluxes and effective moisture diffusivities. The starch was plasticized using glycerol and xylitol either individually or in 1:1 combination. The water migration fluxes and moisture diffusivities were higher in xylitol plasticized films compared to the glycerol plasticized ones. For low plasticizer concentrations, the presence of both the plasticizers competitively reduced the effective moisture diffusivities and moisture migration fluxes due to antiplasticization. However, at higher plasticizer contents (at and above 15 wt%), the presence of multiple plasticizers enhanced the moisture migration fluxes and effective moisture diffusivities due to synergistic plasticization. The moisture migration fluxes and effective moisture diffusivities exhibited both moisture and plasticizer concentration dependence and the former was found to be stronger than the latter. These findings can be used for designing and controlling the vapor barrier properties of starch-based bioplastics during drying and formulation phase.